<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"> 
<title>CSS基本语法</title> 
<style>
p:after{
    content:url("smile.png");
}
</style>
</head>

<body>
    <p>每个段落后添加img</p>
    <p>每个段落后添加img</p>
    <p>每个段落后添加img</p>
</body>
</html>